Systems exist for attaching accessories to threaded firearms barrels, such as found on the AR-15. However, the method in which accessories are attached is limited to three general solutions. One solution is to provide female threading on the accessory to attach to the threaded barrel, but this results in limited or no indexing, wherein indexing consists of rotating a device such as a sight around the barrel. When a state of the an female threaded device is attached to a male threaded bore, the rotational position of the device relative to the gun barrel is set wherever the threads align to provide a tightened fit. A second solution is to attach the accessory rearward on the barrel but this puts the front sight too close to the rear sight, which sacrifices accuracy. The standard AR-15 comes affixed with, a sight clamped to the barrel at the recoil gas port which does not provide a proper sight radius for maximum precision. As handguard development proceeded handguards became long enough to cover the gas port, which provided a third general solution. In the event of a handguard covering the gas port a front sight is attached to the handguard instead of the barrel. While the handguard is customizable and allows options for attaching the front sight, this solution also has problems. Attaching a front sight to an extended handguard allows for misalignment relative to the bore of the firearm when forces are applied to the handguard because the handguard moves relative to the bore of the firearm. Although this relative movement is minimal, the effects on aim can be compounded at long distances. To provide a truly accurate accessory, the accessory and the bore of the firearm must never move relative to each other. However, with AR-15s, the firearm bore comes in a wide variety of outside diameters, so that accessories are not available that fit around the barrel. This is an issue with sights, because it prevents continuous indexing. Silencers and other devices that attach to a bore do not provide a consistent attachment surface that properly provides the ability to attach a wide variety of accessory products, such as sights.
Current products do not allow accessories to be fixed to the barrel at any angle around the bore of the firearm, referred to herein as continuous indexing, which limits the user of the firearm to few angles for accessory mounting. Current methods of attachment involve threading a muzzle device to a gun barrel while sandwiching a crush washer. A shooter wanting to rotate the muzzle device to a different angle must loosen the muzzle device and remove the muzzle device and then replace the crush washer. Further, this method involves different torque on the muzzle device depending on the angle, not guaranteeing an appropriate torque can be achieved at the desired angle. This is because, when threading the muzzle device, the point of optimal tension created by the threading does not necessarily match up with the desired angle for the muzzle device. Further, if the muzzle device is to be realigned then a new crush washer must be used. Spacing washers can also be used to create a correct index angle for the accessory but must also be replaced if a new angle is desired. If an accessory needs to be indexed rapidly and efficiently neither crush washers or spacing washers provide the ability to do so.